subjective pronoun in the nominative predicate

[risby]

Talk about a title to scare people off, eh?

A mate of mine reckons

"to be" [...] is unique in that it implies equality. As we know from maths class, "If A = B, then B = A". In English, this correlates to "If A is B, then B is A". This implies that if we use pronouns on either side of any usage of the verb "to be", the pronouns should be nominative/subjective, not objective.

Specifically, when we use "to be", pronouns should be subjective: I, he, she, we, they; not objective: me, him, her, us, them.

Abuse: It's me.
Correction: It's I.
Reverse to prove: "I am it."; not "Me am it."

Abuse: The winners should be us.
Correction: The winners should be we.
Reverse to prove: "We should be the winners."; not "Us should be the winners."

Abuse: The most qualified is her.
Correction: The most qualified is she.
Reverse to prove: "She is the most qualified."; not "Her is the most qualified."

"The winners should be we" and "The most qualified is she"!

This seems bizarre to me. I've never heard anyone speak like this and I'm not about to adopt this rule for fear of seeming a numpty. Can someone please confirm this rule and examples.

[susiedqq]

You are correct. Don't attempt to flip, or you will flop

[Tdol]

Traditional grammars would agree with your friend as they say that copular (linking) verbs can't take object pronouns. However, this does fly in the face of general usage. I would never say 'It is I.'

[risby]

I would never say 'It is I.'

Except perhaps in answer to the question:

"Is it you that has the solution to the square root of minus one?"